Power converters, such as AC-to-DC and DC-to-DC converters, are known in the art. A design technique generally referred to as xe2x80x9cmultiphasingxe2x80x9d, wherein two or more switching converter stages are connected in parallel (e.g., xe2x80x9cinterleavedxe2x80x9d) to deliver power through a common output terminal, has emerged to try to alleviate the shortcomings of single-phase converters. Traditionally, such polyphase interleaved power converters have utilized a fixed number of phases to achieve the power conversion. The specific phase number is fixed to match the needs of any given application or design constraints. That is, the phase number is uniquely fixed e.g., two, three, twelve, etc.
In polyphase interleaved converters, the magnitude of the AC component of the input and output currents is functionally related to both the phase number and the PWM (Pulse-Width Modulation) duty cycle. As the PWM duty cycle changes, the magnitude of the AC component will also change. For example as shown in FIG. 1, whenever the PWM duty cycle matches the ratio of the low-side voltage of the converter relative to the high-side voltage of the converter, the AC component of the input current of the converter will have a minimum value in amplitude. FIG. 1 further illustrates the effect of phase number, not just at such minimum values of amplitude, but over the full-range of values that the duty cycle may take, e.g., duty cycle values ranging from zero to one. It can be shown that the relationships depicted in FIG. 1 between duty cycle and phase number are also equally applicable relative to the output current of the converter.
Since in any practical converter circuit the PWM duty cycle may be subject to variation due to environmental and/or operational conditions to which the circuit may be exposed to, it would be desirable to provide a converter and power conversion techniques that would allow reducing the AC component of the input and output currents regardless of variation of the PWM duty cycle.
Generally, the present invention fulfills the foregoing needs by providing in one aspect thereof, an interleaved converter including a plurality of phasing stages. The converter further includes a calculator configured to calculate a duty cycle value of the converter. A processor is configured to receive the calculated duty cycle value. A rulebase is coupled to the processor and includes a set of phase-selection rules configured to select a respective phase number based on the calculated duty cycle value.
The present invention further fulfills the foregoing needs by providing in another aspect thereof, a method for controlling an interleaved converter. The method allows providing a plurality of phasing stages. The method further allows calculating a duty cycle value of the converter. The calculated duty cycle value is processed relative to a set of phase-selection rules. A respective phase number is selected based on the calculated duty cycle value.